Method of producing colored films



Patented Nov. 5, .1929 i UNITED- STATES PATENT OFFICE ROBERT F. ELDER, 01 LOS ANGELES, CALIFORNIA, ASSIGN OR TO BINOCULAR STEREO- SCOPIC FILM COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF CALI- FORNIA.

METHOD OF PRODUCING COLORED FILMS Application filed March 22, 1926. Serial No. 96,658.

This invention relates to the coloring of motion picture film. In the motion picture industry colored motion pictures are projected by casting upon a screen two images of complementary color value, which images were-taken simultaneously-and from the same viewpoint. In the infancy of the colored motion picture, two separate films were used having the separate color value images upon each film. These two films were placed side by side and the color value images cast on the screen in registry. It is the present practice of certain companies to cement two films together with the emulsion on the outside and the images thereof in registry so that a standard projector may be used for projecting the images to a screen. The images must be colored with different colors after the films have been secured together; otherwise any stretch or shrinkof the films would throw the images out of registry. The coloring of the images is a very delicate matter, since special care must be used to properly color each image and not to get any color used on the images on one side of the film on the oppositeside thereof.

One well known method of coloring film is known as the flotation process. The film is floated on the surface of a body of coloring liquid and the lower face thereof contacts the coloring liquid so that only the images on that side are dyed. After the images on one face of the fil-m have been colored, the film is inverted and floated on the surface of a body of coloring liquid of another color in order to color the images on the other side of the film. In such a process as this there is some liability ofthe color flowing'onto the upper face of the film, thus producing an inferior result which of course detracts from the images projected on a screen. Another undesirable occurrence in this method is that sometimes bubbles will form under the film and portions of the images will hot be entirely and properly colored. This also produces an inferior result. It is desirable to similarly color fil-m for use in projecting stereoscopic images and the above flotation process has been used for that purpose.

It is an object of this invention to provide a method of coloring film in which the lower face of the film engages the coloring liquid with sufiicient pressure to prevent the forming of air bubbles therebelow.

Another object of this invention is to provide a method of coloring film in which it is impossible for the coloring liquid to get onto the upper face of the film during the application of color to the lower face thereof.

It is a further object of this invention to PI'OVldBElIl apparatus for carrying out the above specified methods without depending upon the uncertain and unsatisfactory flotation process.

Other objects and advantages of my invention will be made evident in the following description.

Referring to the drawing in which I illustrate the apparatus of my invention,

Fig. 1 is a longitudinal section of a tank used in the practice of the invention.

Fig. 2 is a cross section taken on the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary partially sectioned view taken as indicated by the arrow 3 of Fig. 2.

Referring to the drawing in detail, the numeral 1.1 represents a platform on which a receptacle or tank 12 is supported. The receptacle 12 is provided with a nipple 13 to which a hose 14 is secured, and by means of which a body of coloring liquid is supplied to and withdrawn from the receptacle 12 from suitable receptacles not shown.

Guides represented at 16 are secured to opposite side walls 17 of the receptacle 12. Each guide 16 consists preferably of upper and lower guide members in the form of angles 18. .Vertical legs 19 of the angles 18 engage and are secured to inner faces 20 of the side wall 17 of the receptacle 12.- Extendin substantially horizontally are horizontal legs 21 of the angles 18 which project parallel to each other and towards the middle of the receptacle 12. The horizontal legs 21 are spaced apart so as to provide a channel 23. The angles 18 are curved or dipped downwardly at their central parts as illustrated best in Fig. 1 and the channels 23 are a by a bracket 28.

1 23 and around the exhaust sprocket 27.

also to cover the frames of the 40 portion of the coloring 50 actual practice An intake sprocket is secured to the left end of the receptacle by means of a bracket 26 and an exhaust sprocket 27 is secured to the right end of the receptacle 12 The numeral 30 represents a film to be dyed. The film 30 is threaded through the dyeing apparatus as illustrated in the drawing. It passes around the intake sprocket 25 through the channel Referring particularly to Figs. 2 and 3, it

will be noted that the distance between the side wall 17 of the receptacle 12 is but slightly 25 channels 23 should be made only wide enough to ermit the film to freely pass therethrough. n utilizing the apparatus the film is threaded as shown in the drawing before any coloring liquid is introduced into the re- 30 ceptacle 12. After the film has been properly placed coloring liquid is supplied to the receptacle 12 through the hose 14; and the nipple 13, thus forming a body of coloring liquid in the receptacle 12. The ends of the chan- 35 nels 23 are at all times above the level of the liquid 35. The body of liquid would ordinarily assume a level as represented by the broken line X-X of Fig. 1 but because of the film 30 being secured as shown the central liquid is displaced so that the upper surface conforms to the curvature of the film. As should be noted from Fig. 1, the upper face of the central portion of the body 35 is caused to occupy a position below the normal level X- X and the upper faces at the ends of the body 35 occupy positions above the normal level X-X. The displacement of the body of coloring liquid 35 is but very slight, and in the coloring liquid is usually displaced not more than one-eighth inch so that the hydrostatic pressure resulting from the displacement will not be very great.

The placing of the pressure on the upper face of the body of liquid in the manner illustrated tends to prevent the forming of air bubbles below the film and therefore an imperfect result from this source will be eliminated. By reason of the fact that the widths of the channels 23 are very near to the thickness of the film 30. the surface tension of the coloring fluid will be strong enough to prevent it from passing around the film through the channels 23 and contact the upper face of the film 30, even though there is a hydrostatic pressure on the liquid. Since the horizontal legs 21 cover the perforations 32 of the film 30, the coloring liquid cannot pzliss therethrough to the upper face of the 1i m.

If the displacement of the coloring liquid is less than one-eighth inch, it is not necessary to cover the perforations because the capillary attraction is enough to prevent the liquid from flowing through them. I have found that the coloring liquid may be displaced more than one-eighth inch without any danger of its passing around the edges of the film if the edges be treated with a water-repellant substance or if the inner faces of the angles 18 be so treated. Another method is'to fill the remaining spaces in the channels (when the film is in place) with a fluid, such as mercury, which has sufficient surface tension to keep it in the channels and not be displaced by the hydrostatic head of the coloring liquid.

After the coloring liquid has been placed in the receptacle 12, as illustrated in lflig. 1, the film is moved continuously through the apparatus of the invention by mechanism, not shown, so that all of the images on the lower face thereof will be brought into contact with the body of the coloring liquid 35.

After this treatment the film may be turned over and passed through an identical apparatus filled with liquid containin dye of a different color, and the opposite ace of the film colored as desired.

The invention provides a method of coloring film in which the lower face of the film is engaged with the body of liquidunder slight hydrostatic pressure in such a manner that no coloring liquid can come into contact with the upper face of the film.

My invention, as shown, and clearly evident from the foregoing description, differs from the ordinary flotation process in that the film is forced against the upper surface of the liquid with a material pressure so as to produce better results by excluding air bubbles and assuring a proper adhering of the color. In the present methods the film is not caused to engage the body of coloring liquid under any material pressure but the film merely floats along the top thereof. Another important feature of the invention is the apparatus for carrying on my invention. The guides 16 are very important since they guide the film into proper contact with the body of liquid and prevent the liquid from flowing-into contact with the upper surface of the film.

I claim as my invention:

1. An apparatus for coloring film consisting of: a receptacle for retaining a body of coloring liquid; and means for guiding a film so that said body of coloring liquid will be displaced by said film, the lower face of said film contacting said body of coloring liquid,

said means being so formed that said body of coloring liquid cannot contact the upper face of said film and com rising complemental guides forming channe s into which the edges of said film extend, said channels being of such a size that surface tension of said coloring liquid will prevent said coloring liquid from passingthrough said channels around the edges.

2. An apparatus for coloring film consistmg of: a receptacle for retaining a body of coloring liquid; and means for guiding a continuously moving film so that said body of coloring liquid will be displaced by said film, the lower face of said film contacting said body of coloring liquid, said means being so formed that said body of coloring liquid cannot contact the upper face of said film and comprising I guides having channels into which the edges of said film extend, said channels being of such a size that surface tension of said coloring liquid will prevent said col oring liquid from passing through said channels around the edges, said guides covering the perforations of said film.

3. An apparatus for coloringfilm consisting of: a rece tacle for retaining a body of coloring liquit and guides secured to said receptacle for guidin the lower face of said film into contact wit said liquid in such a manner that the bod of liquid is displaced by said film, the ends of said guides-being above the normal level of said liquid and the centers of said guides being below the normal level of said liquid, and preventing said liquid from reaching the upper side of said film.

4. An apparatus for coloring film consisting of: a receptacle for retaining a body of coloring liquid; and guides secured to said receptacle providing film-guiding channels adapted to guide the edges of said film, the ends of said channels being above the normal level of said liquid and the centers of'said channels being below the normal level of said liquid, said channels preventing said liquid from reaching the upper side of said film.

5. An apparatus for coloring film consisting of: a receptacle for retaining a body of coloring liquid; and guides secured to said receptacle providing film-guiding means adapted to guide the edges of said film, the ends of said guides being above the normal level of said liquid and the centers thereof being below the normal level of said liquid, said guiding means preventing said liquid from reaching the upper side of said film.

6. An apparatus for coloring film consisting of: a receptacle for retaining a body of coloring liquid; and means secured to said receptacle providing film-guiding channels adapted to guide the edges of said film, the ends of said channels being disposed above the normal level of said liquid and the centers of said channels being disposed below the normal level of said liquidto prevent said lfilguid from reaching the upper side of said 7. An apparatus for color-ing one face only of a continuous film, comprising: a receptacle containing a body of coloring liquid; and complemental guide members for supportin a moving film at the top of said receptacle an for shielding the marginal edges thereof, said guide members being adapted to hold and force the intermediate portions of the lower surface of said film with material pressure against the upper surface of said liquid to effect a proper adhering of the coloring fluid.

8. An apparatus for treating one face only of a continuous film, comprising: a receptacle for retaining a body of liquid; and complemental guide members for supportin a m0ving film through said receptacle and s ielding the marginal edges thereof, said guide members being adapted to hold the intermediate portions of the film against the upper surface of said liquid with material pressure to effect a proper adhering of the coloring liquid and to prevent said liquid from reaching the upper side of said film.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 16th day of March, 1926.

ROBERT F. ELDER. 

